Labyrinth seal for axial flow fluid machines

ABSTRACT

A sealing device in a turbine for preventing excessive leakage of motive fluid between a stator and the tips of rotor blades, the leakage being from a high-pressure side to a low-pressure side, including an airfoil provided on the outer periphery of each rotor blade with the airfoil being skewed to pump the leakage fluid back to the high-pressure side.

United States Patent Fred J. Cross, 11-.

Glastonbury, Conn.

Dec. 5, 1968 Apr. 20, 1971 I The United States of America as represented by the Secretary of the Navy [72] Inventor [21 Appl. No. [22] Filed [45} Patented [73] Assignee [54] LABYRINTH SEAL FOR AXIAL FLOW FLUID MACHINES 1 Claim, 3 Drawing Figs.

[52] 11.5. 111 415/172, 4l6/174,416/191 [51] IlnLCI F0ld5/20 [50] FieldofSearch 253/773,

77(S1); 103/111 (C3);415/172,168,169,170, 173,174;416/19l,192, 174

[56] References Cited UNITED STATES PATENTS 2,278,041 3/1942 Allen 2,510,734 6/1950 Bodger 416/190 3,185,441 5/1965 Reuter 416/190(X) 3,377,050 4/1968 Guy 416/190 1,568,034 12/1925 Losel 253/77(.3)

3,447,741 6/1969 Havette et a1 230/ l 22(A) FOREIGN PATENTS 134,451 10/ l 929 Switzerland 253/77( .3)

Primary Examiner-Everette A. Powell, Jr. Att0rneysEdgar .l. Brower, H. H. Losche and Paul S.

Collignon ABSTRACT: A sealing device in a turbine for preventing excessive leakage of motive fluid between a stator and the tips of rotor blades, the leakage being from a high-pressure side to a low-pressure side, including an airfoil provided on the outer periphery of each rotor blade with the airfoil being skewed to pump the leakage fluid back to the high-pressure side.

PUMPING ACTION HIGH PRESSURE STAGE LOW PRESSURE STAGE PATENTEDAPRZOIHH 3;575523 ROTATION l9 l3 J FIG. I

- .6 1 PUMPING n cnou l2 HIGH LOW I PRESSURE PRESSURE STAGE STAGE -FIG.2

ROTATION INVENTOR F.J.GROSS,JR.

ATTORNEYS.

LABYRINTH SEAL FOR AXIAL FLOW FLUID MACHINES I BACKGROU N D OF THE INV ENTION The present invention relates to a labyrinth seal for axial flow fluid machines, such as axial flow compressors and turbines of gas turbine engines. Labyrinth seals are used to minimize leakage of gas between relatively rotating parts in devices where direct contact seals are not feasible. These seals are frequently used between the stator and the rotor structure of compressors and turbines.

One such labyrinth seal for a turbomachine is shown and described in US. Pat. No. 3,251,601, which issued May 17, 1966 to Robert R. Harvey. This patented device reduces the effective clearance and the effective leakage area of the labyrinth seal throat by the dynamic effect of a stream of air or gas directed radially of the seal and transversely to the direction of leakage flow. The face of the turbine blades are modified to provide a vane which amounts to a centrifugal fan which during rotation of the turbine blades will circulate the air or other gas within the chamber radially outwardly.

Another sealing arrangement for turbomachines is shown in US. Pat. No. 2,685,429, which issued Aug. 3, 1954, to Earl L. Auyer. In this device, an annular shroud member surrounds the tips of the turbine blades and is radially spaced from the tips to provide sufficient mechanical clearance to avoid rubbing of the tips against the shroud. A fluid dam in the clearance space between the inner surface of the shroud and the blade tips is provided by introducing a jet of fluid in an upstream direction. This is accomplished by providing a circumferentially extending slot in the shroud. This slot is angularly disposed with respect to the inner surface of the shroud to form a restricted fluid passageway through which a jet of fluid is introduced into the clearance space at a location between the leading edges and the trailing edges of the turbine blades.

SUMMARY OF THE INVENTION The present invention provides an improved yet relatively inexpensive device for preventing excessive leakage of fluid between the tips of the rotor blades and the stator. An airfoil is provided on an outer rim which is integral with the turbine blade, and the airfoil is skewed so as to provide pumping action when the blade is rotated. Each rotor blade is provided with an airfoil and upon rotation of the rotors these airfoils pump the leakage fluid back to the high-pressure side of the machine.

It is therefore a general object of the present invention to provide a new and improved sealing arrangement for a turbomachine which minimizes the leakage of motive fluid past the tips of the rotor blades.

Other objects and advantages of the present invention will be readily appreciated as the same becomes betterunderstood by reference to the following detailed description when considered in connection with the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a top plan view showing an airfoil on the rim of a rotor blade;

FIG. 2 is a side view, partly in section, showing a preferred embodiment of the present invention; and

FIG. 3 is a top plan view showing another configuration of an airfoil on the rim of a rotor blade.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawing, there is shown a blade 11 which is one of a plurality of rotor blades of a turbine. These blades 11 are carried by a rotor which is rotatably supported by suitable bearings (not shown) in a manner well known to those skilled in the art. A rim 12 is provided on the outer end of each blade 11 and an airfoil 13 is provided on the outer surface 14 of rim 12. By way of example, blade 11, rim 12 and airfoil 13 might be either cast or machined as one unit to provide sufficient strengh when the rotor is driven at high speed.

As est shown in FIG. 2 of the drawing, a stator 15, which might be annular in configuration, surrounds the rotor. A pair of flanges l6 and 17 are provided on the inner surface of stator and a clearance space 18 is provided to allow blades 11 to rotate relative to stator 15. It is through this clearance space 18 that some motive fluid passes without performing useful work on blades 11. In order to minimize this leakage, airfoil 13 is skewed with the airfoil 13 beginning at the leading edge 19 of rim l2 and being skewed toward the high-pressure stage of the machine. When blades 11 are rotated, airfoil 13 provides a pumping action and leakage air is pumped back to the high-pressure stage.

In the embodiment shown in FIG. 1 of the drawing, the sides of airfoil 13 are straight and parallel and the upper extending surface is in the shape of a rhomboid. Another configuration of an airfoil is shown in FIG. 3 of the drawing, wherein the sides of airfoil 21 are curved and no two sides are parallel.

OPERATION In operation, motive fluid flows from a high-pressure stage through blades 11 to the low-pressure stage thereby driving the turbine rotor. As it is necessary, however, to have clearance 18 between the ends of blades 11 and stator 15, any fluid passing through clearance 18 will not perform any useful work on blades 11 and thus will reduce the overall efficiency of the machine. The airfoils on the ends of blades 11, however, provide a pumping action which pumps or forces leakage fluid back to the high-pressure stage thereby minimizing leakage and providing for a more efficient machine.

It should be understood, of course, that the foregoing disclosure relates to only a preferred embodiment of the invention and that numerous modifications or alterations may be made therein without departing from the spirit and scope of the invention.

Iclaim:

1. A sealing device for an axial flow fluid machine comprising:

a stator member,

rim on the outer periphery thereof, said rim having trailing and leading edges, said rotor member being rotatably mounted and spaced relative to said stator member to provide running clearance, said running 5 clearance providing a passageway for motive fluid from a high-pressure stage of said axial flow fluid machine to a low-pressure stage, and

a single airfoil on the outer periphery of each rim extending from the trailing edge to the leading edge of said rim, said airfoil having an upper extending surface comprised of nonparallel sides and being skewed relative to the direction of travel of said motive fluid through said passageway whereby said airfoils pump said motive fluid passing through said passageway back to said highpressure stage of said axial flow fluid machine.

a rotor member having a plurality of blades each having a 

1. A sealing device for an axial flow fluid machine comprising: a stator member, a rotor member having a plurality of blades each having a rim on the outer periphery thereof, said rim having trailing and leading edges, said rotor member being rotatably mounted and spaced relative to said stator member to provide running clearance, said running clearance providing a passageway for motive fluid from a high-pressure stage of said axial flow fluid machine to a low-pressure stage, and a single airfoil on the outer periphery of each rim extending from the trailing edge to the leading edge of said rim, said airfoil having an upper extending surface comprised of nonparallel sides and being skewed relative to the direction of travel of said motive fluid through said passageway whereby said airfoils pump said motive fluid passing through said passageway back to said high-pressure stage of said axial flow fluid machine. 